Separatory apparatus



June 14, 1955 E. c. HERKENHOFF SEPARATORY AFPARATUS 4 she'ts-sneet 1 Filed Oct. 1, 1953 INVENTOR BY M ATTORNEYS June 14, 1955 E, c. HERKENHOFF 2,710,691

SEPARATQRY APPARATUS Filed Oct. 1, 1953 4 Sheets-Sheet 2 INVENTOR ATTORNEYS June 14, 1955 Filed Oct. 1, 19253 E. C- HERKENHOFF SEPARATORY ARPARATUS Ag. 6. /4 M 9% 67)! "4 Sneaks-Sheet :5

ATTORNEYS June 14, 1955 E. c. HERKENHOFF 2,710,691

SEPARATORY APPARATUS Filed Oct. 1, 1953 4 Sheets-Sheet 4 INVENTOR Gael, BY Oahu,

ATTORNEYS United States Patent 0 F SEPARATORY APPARATUS Earl C. Herkenhoif, Hibbing, Minn., assignor to Pickands Mather & Co., Cleveland, Ohio, a copartnership Application October 1, 1953, Serial No. 383,555

' 10 Claims. (Cl. 209-223) This invention relates to the art of beneficiating ore ;5

materials, and, more particularly, to the art of recovering mineral values and reforming a heavy medium from the products obtained by a sink-float procedure using as heavy medium a suspension of finely subdivided relativelymagnetic mineral such as magnetite. tion is particularly concerned with recovery of the solids components of the heavy medium for re-use in the process. While not restricted thereto, the invention will be described with particular reference to the working-up of a sink-float product or cyclone separation pulp comprising fine magnetite medium and relatively coarse hematite ore.

In processing a sink-float product or cyclone separation pulp comprising fine magnetite medium and coarse hematite ore it is broadly old to separate the fine magnetite from the same by the use of a wet drum-type magnetic separator such as the well-known Stetiensen magnetic separator. in such operation the operator sets the spigot openings to pass the coarse non-magnetic fraction while still endeavoring to keep the drum of the magnetic separator properly submerged. However, the spigot load, i. e., the proportion of non-magnetics to magnetics, and the volume of feed tend to vary from period to period, with consequent variation (1) in the level of the liquid in which the drum of the magnetic separator is (or should be) submerged and hence (2) in the efiiciency of the magnetic separation. Moreover, in the subsequent dewatering step the fine magnetite, which through poor efficiency of magnetic separation had been carried forward with the non-magnetic portion, tends to be carried ofi in and discarded with the waste water.

A principal object of the present invention is the provision of means for insuring proper submergence of the drum of the wet-type magnetic separator under all variations and fluctuations of feed and of spigot load. Another at The inveniii) object of the invention is to overcome the diificulties incident to a variable spigot load of non-magnetic material which varies with the tonnage of material to the circuit and the weight split between the sink material and the float material as the specific gravity of the separating medium changes and as the character of the ore changes. A further inventive object is to improve the recovery of the solids, e. g., the magnetic material of the heavy medium. Another inventive object is to provide for magneticcleaning of the waste water whereby to recover any magnetite fines which may have been entrained with the non-magnetic portion passed by the wet-type magnetic separator.

According to the present invention a wet drum-type magnetic separator, suitably modified, is mounted above the pool end of and preferably directly on a classifying and dewatering device into which latter the non-mag neticportionof the feed passed by the magnetic separator directly discharges. By suitably modified" is here meant that the lower box, and associated spigots,. underlying the feed plate of a conventional Stefiensen Wet drum-type magnetic separator, are removed leaving a suitable slot or elongated aperture in, and adjacent the Zfllfififil Patented June 14, 1955 bottom of, the feed plate for downward passage of coarse tailing (i. e., the non-magnetic portion of the feed) into the body of liquid occupying the underlying tank. The drum of the magnetic separator is so positioned with respect to the level of liquid maintained in the classifier during use as to insure proper submergence of the drum in said liquid.

The adapted wet drum-type magnetic separator used may be of the concurrent revolution drum type or the counter revolution drum type. One, or more-preferably two-magnetic separators can be employed per classifier, and can be disposed either transversely or, preferably, longitudinally of the major axis of the classifier. Preferably in adapting the counter revolution type separator not only are the box and coarse tailing spigot omitted but also the overflow weir end of the feed plate is preferably extended slightly higher than conventionally so that the overflow tailing of the separator discharges into a launder located outside of the classifier.

Where a pair of adapted separators are mounted longitudinally of the classifier, the separators may be so disposed that the two feed manifolds and the two concentrate launders are located outside, and on either side of, the classifier tank, and the two overflow weirs discharge into a common overflow launder located between the separators. In the alternative, the feed manifolds may be located between the separators and each of the two overflow weirs discharge into a separate overflow launder located outside and alongside of the classifier tank.

The invention Will now be described in greater particularity and with reference to the appended drawings, in which:

Fig. 1 is a somewhat schematic plan view of a preferred form of apparatus in accordance with the invention;

Fig. 2 is a side elevational view of the apparatus illustrated in Fig. l, with driving motors and associated mechanism omitted in the interest of clarity;

Fig. 3 is an end elevation of the apparatus, as viewed from the left of Fig. l and with driving motors omitted;

Fig. 4 is an enlarged, somewhat schematic sectional elevation taken on line 44 of Fig. 1;

Fig. 5 is a view similar to Fig. 4 but illustrating concurrent feed to the magnetic drum assemblies;

Fig. 6 is a fragmentary end elevation and in partial section illustrating a further modification of the invention;

Fig. 7 is a fragmentary plan view of the modified form of apparatus shown in Fig. 6;

Fig. 8 is a fragmentary side elevation of the apparatus shown in Figs. 6 and 7 viewed in the direction of the arrow, small a of Fig. 7; and

Fig. 9 illustrates a still further embodiment of apparatus according to the invention in which a traveling belt or conveyor is substituted for rotating drums.

In the embodiment illustrated in Figs. 14, parts of a pair of drum-type wet magnetic separators are integrated with a classifier, the feeds to the separator drums being countercurrent, and there being a single overflow launder common to the two magnetic separators. According to this embodiment, an inclined, trough-bottomed classifier tank 16, mounted on suitable supports 11, is provided with an inclined rotatable Archimedes screw, or "spiral, 12 which is supported at its ends by conventional bearing supports and disposed in and generally parallel to the bottom of the trough .of the classifier tank after the manner of the well-known Akins classifier. Conventional means (not shown) are provided for rotating the spiral. As is shown in the drawing, the high ends of the inclined tank bottom and of spiral 12 extend above the remainder of tank 10 and are adapted to discharge a generally de-watered, particulate, solid product from the high end of said tank.

Over the pool (i. e., the low) end of tank 10 and adjacent the side walls of the latter there are mounted two magnetic drum assemblies D and D' which are allo chirally identical and hence a description of one will suflice for both. Assembly D includes a horizontally disposed water-tight metal drum 14 the shaft 15 of which is supported by and rotatable in bearing members 16 and 17. Bearing member 16 may, as shown, be mounted on the reinforced upper edge of the end Wall 18 of tank 10, while bearing member 17 may be mounted on a suitable supporting member 19 extending inwardly from the side of tank 10. Drum 14 houses within it stationary magnet means 29 (shown in Fig. 4) conventional for a drum-type wet magnetic separator. Rotation of drum lit is effected by means of driving motor 21 and chain-and-sprocket assembly 22.

Assembly D also includes a horizontally disposed feed plate 23 which is positioned beneath and is coextensive in length with drum 10, and is generally complemental in cross-section to the peripheral surface of said drum to define an arcuate space 24 between said feed plate and said drum. Feed plate 23 is provided with an aperture 25 in the lower portion thereof giving direct communication between arcuate space 24- and the interior of the pool end of tank 10.

The height of. the pool end of tank 10 and the level at which the drum assembly is mounted thereover are so chosen with respect to the level of the spiral 12 as to insure the existence of a substantial space (vertically measured) between aperture 25 and the upper surface of spiral 12 amply sufiicient for proper settling of solids through the pool and distant from the magnetic field.

Assembly D further includes means for feeding aqueous slurry into space 24, and means for collecting concentrate separated from said slurry by the attractive force of said magnet means. The former comprises a feed box 26 and a plurality of spaced feed conduits 27, 27 communicating between the bottom of feed box 26 and feed openings 28, 28' let into feed plate 23. According to this embodiment in which the direction of feed flow is counter to the direction of rotation of drum 14, the feed openings 28, 28' are located between aperture 25 and the trailing edge of feed plate 23 with respect to drum 14, i. e., at loci near the cut-off line of the attractive force of magnet means 29. The illustrated means for collecting concentrate includes an inclined lip member 29 whose upper edge is associated with the trailing edge of feed plate 23 and which extends outwardly of the same over the edge of the side wall of tank 10, a scraper 30 contacting drum 14 at a line therealong overlapping the upper edge of lip member 29 and outside the zone of attractive force of magnet means 20, and a concenirate launder 31 underlying the outwardly extending lower edge of lip member 29 and positioned and adapted to receive from the latter moist concentrate delivered thereto from drum 14 by means of scraper 30. As shown, feed conduits Z7, 27 extend through openings 32 let into lip member 29 with which openings the conduits make a tight fit.

In lieu of scraper 30 there may be employed a water spray or sprays, the showing of a scraper being illustrative only of conventional means for removing attached concentrate from the magnetic drum.

Associated with the near edge 33 of feed plate 23, which extends well beyond the line, along drum 14, at which attractive force of magnet means 29 first becomes apparent, is a horizontally disposed overflow launder 34 for collecting and drawing off from the apparatus overflowing water and fine sands. As shown, a single overflow launder is common to assemblies D and D. The near edges 33, 33 of feed plates 23, 23' and associated upper edges of overflow launder 34 constitute a pair of adjustable weirs which determine the level of a body of liquid maintainable in tank 10 and, during use of the apparatus, maintain a constant level of liquid in tank 10. Feed plates 23, 23' largely lie below said liquid level and, hence, in use are mostly submerged in such liquid.

r Likewise, a minor but substantial portion of the peripheral surface of each of drums 14 and 14' lies below said liquid level; hence, in use, the drums are partially submerged,

In the operation of the apparatus just described, tank 16 is filled with aqueous liquid to level 33. Drum 14 is set into rotation in the direction indicated by the arrow, magnet means 20 is actuated and spiral 12 is set into rota tion. An aqueous slurry or pulp, containing relatively coarse, relatively non-magnetic solid particles (e. g., hematite ore particles) and relatively fine magnetic particlcs (c. g., iine magnetite), is continuously fed from feed box 26. through feed conduit 27, into arcuate space 24 and into the sphere of attractive force of magnet means 20. The direction of movement of the feed pulp or slurry, in space 24, is contrary to the direction of rotation of drum 14 and through the zone of attractive force. to promote attraction of magnetic particles, present in the slurry, to, and attachment thereof onto, the surface of drum 14 and movement of such attracted particles out of the zone of attractive force and towards and to scraper 3G, by which latter they are removed from the drum surface, falling upon lip member 29 and moving thereover into concentrate launder 31.

The eountercurrent feed moves through space 24 until it reaches aperture 25, at the lowest portion of submerged feed plate 23, whereupon those non-magnetic solid particles which have not been attracted to drum 14 sink through aperture 25 directly into the body of aqueous liquid maintained in tank 10 and gradually settle therein into the zone of influence of rotating spiral 12 and are moved by the latter upwardly along the inclined bottom of tank 1i! and discharged from the latter. Simultaneously, liquid is added, from the feed, to the body of liquid in tank 10, necessitating a corresponding overflow of the latter. Since the weir 33 determines liquid level in the tank, the overflow of water and fine sands inevitably takes place by way of aperture 25, that portion of arcuate space 24 between drum 10 and the near edge of feed plate 23, over weir 33 and into overflow launder 34. This enforced course brings any solids, tending to overflow with the water, a second time into the zone of attractive force of magnet means 20 and hence makes possible the salvaging of fine magnetic particles which may have been entrained with the non-magnetic particles and carried by the latter downwardly into or through aperture 25.

The position of weir 33 being constant, the liquid level is maintained constant and hence the extent of submergence of the peripheral surface of drum 14 is maintained constant regardless of variations in the rate of introduction of the feed and/or in the composition or structure of the feed.

it so desired, the eountercurrent type of construction shown in Fig. 4 can be altered, by reversing the direction of rotation of the drum, substantially raising the leading edge of the feed plate and allochirally reversing the position of the feed box, feed conduits, concentrate scraper, inclined lip member and concentrate launder with respect to the feed plate, so that both the concentrate launder and the overflow launder are disposed between the pair of magnetic drums, the concentrate launder being superimposed over the overflow launder. This alternative construction, while permitting use of a single concentrate launder, common to a pair of magnetic drums, instead of plural concentrate launders as described above, is less preferable than the above-described construction.

The above embodiment may be modified to the extent of substituting concurrent magnetic separation for the eountercurrent separation of Figs. l-4. Such substitution is illustrated in Fig. 5. According to the latter, in which magnetic drum assemblies E and E are allochiral duplicates of each other, a feed trough 50 coextensive in length with feed plate 23 is operatively associated with the near edge of the latter so as to constitute said near edge an inlet weir S1 for the incoming aqueous pulp or slurry. Lip member 52, similar to lip member 29 of Figs.

1'-4, is associated with the trailing edge of feed plate 25 and overlies concentrate launder 31 so as to divert into the latter solids removed from the peripheral surface of drum 14 by the action of scraper 30. Underlying the trailing portion of feed plate 23 and spaced from the latter is an inclined plate member 53, coextensive in length with feed plate 23, whose upper edge extends beyond and is bent over the edge of the side wall of tank to provide an overflow weir 54. An overflow launder 55 is disposed beneath the bent-over upper edge of plate member 53 to receive water and fine sands overflowed over weir 54. The lower edge or" inclined plate member 53 extends to but not through the space directly beneath aperture 25 in feed plate 23.

In this embodiment, the liquid level within tank 10 is defined by the pair of overflow weirs 54, 54', which serve to insure a constant degree of submergence of drums 14, 14'. Overflow of water and fine sands from tank 10 being by way of the space between the bottom of feed plate 23 and inclined plate member 53, the inevitable movement of liquid towards said space creates turbulence in the liquid body and descending solids immediately beneath aperture 25 thereby tending to dislodge from the coarser non-magnetic particles any fine magnetic particles inadvertently entrained with the former and to move such dislodged magnetic particles into the zone of attractive force of the magnet means.

As will be readily appreciated, feed troughs and 50 may be made unitary without alteration in the operation of the apparatus. In such case, the plural feed pipes 56, 56 shown in Fig. 5 may be replaced by a single feed pipe.

One may, if desired, disassociate the tank overflow means from the magnetic separators. This modification is illustrated in Figs. 68, accordiing to which an adjustable overflow weir 60 is provided in a side wall of tank 10 at a locus remote from the magnetic separators. Weir 69 may, as is well understood, be made sectional (as shown in Fig. 8) to provide for adjustment in the height of the liquid level being maintained in tank 10 and hence for adjustment in the maintained extent of submergence of the magnetic separator drums. As will be understood, the weir may be located at the end of the tank, instead of at the side thereof, if so desired.

Also, as shown in Fig. 6, concurrent flow of feed and constitute said'near edge an inlet weir into the generally arcuate space (24, Fig. 6) between the feed plate and the peripheral surface of the magnetic drum (14', Fig. 6), and movesin said space-towards the trailing edge portion of the feed plate. At the lowest point in the feed plate an aperture or slot 25 is provided, for direct down: ward movement of non-magnetic materials from said space into the body of liquid maintained at constant level within tank 10. Magnetic particles attracted to the peripheral surface of drum 14 are removed from the latter by means of scraper 3t) and fall onto inclined lip member 63 and move thence into concentrate launder 31.

The construction according to this embodiment insures that the extent of partial submergence of the magnetic drums is maintained constant regardless of changes in the rate of introduction of the feed and in its composition.

The identities of the fine magnetic particles and the relatively coarse non-magnetic particles are not critical. The magnetic particles may be magnetite or ferro-silicon or a mixture of the two. The non-magnetic particles may be ore or ore material or other solid particles.

It is to be understood that the invention is notrestricted to the use of a pair of magnetic drums and their appur tenances, it being within the scope of the invention to associate a single magnetic drum assembly or more than 5 two such assemblies with a dewat'e ring classifier. It is to be understood also that it is within the scope of the invention to dispose the magnetic drum assembly or assemblies transversely or obliquely with regard to the long axis of the classifier; also to substitute water sprays-or other known means-f0r the concentrate scrapers shown in the drawing.

The advantages of the construction according to th present invention are many. The construction overcomes the serious difliculties of a variable spigot load of nonmagnetic material which varies with the tonnage of material to the circuit and the weight split between sink material and float material as the specific gravity of the separating medium changes and as the character of the ore material changes. It insures that the magnetic drum is constantly submerged to the desired extent, and hence that magnetic recovery is higher. Any fine magnetic particles inadvertently adhering to the non-magnetic fraction passed initially by the magnetic drum have an opportunity to be scrubbed oif in the spiral and can be overflowed in proximity to the magnetic field and recovered (double cleaning). The apparatus affords a saving in head room, and is cheaper to construct than are separate magnetic separators and dewatering classifiers.

In the embodiment illustrated in Fig. 9, parts of a wet belt-type magnetic separator are integrated with a dewatering classifier to provide an apparatus enjoying some or all of the above-recited advantages of the invention. According thereto, a magnet means 70 and endless belt '7 of substantial width are arranged transversely with respect to and asymmetrically of tank 10 in such manner that the discharge end of the magnetic separator organization extends over one side of the tank while a part of the lower flight of belt 7'1 is disposed below the normal Water level-indicated at 33rnaintained in tank 10 by means of an adjustable weir-not shown in the drawing located in the upper portion of the lower end wall of the tank. An arcuately shaped feed plate 74, 75, coextensive with the width of belt 71 and generally complemental in cross-section to the peripheral surface of the lower flight of belt 71, is arranged beneath and somewhat spaced from the lower flight of belt 71 to define between the feed plate and the belt an arcuate space 76. As shown, the parts 74 and 75 of the feed plate are separated from each other to define a gap 77 adjacent the lowest portion of the feed plate, through which gap direct communication is had between space 76 and the interior of tank 10.

Belt 71 is supported on driven roller 78 and roller 79, and, in use, is maintained in close contact with the lower surface of magnet means 70 by a conventional tightener roller 80 which is weighted or spring-loaded by conventional means (not shown). As illustrated, the lower flight of the belt moves from left (the inlet end of space 76) to right (the discharge end of space 76). At the inlet end of space 76 there is provided a feed trough which is attached to the upper, outer, edge of feed plate 74 and forms with the latter a feed weir 82. A conventional feed pipe 83 for delivering feed to feed trough 81 is indicated at 83.

The upper, outer edge of feed plate 75 is bent over the side of tank It to provide a discharge lip 84, which latter is disposed above and in discharging relation to a concentrate launder 31 arranged outside tank 10. A conventional water spray means, indicated at 85, is provided adjacent the discharge end of space 76 for removing con- ;intrate from belt 71 and directing the same into launder Space 76 is bounded as to its top and its bottom by the belt 71 and feed plates 74, 75, and at its sides by a pair of vertical side walls 86 the lower portions of which extend beneath the normal water level in tank 10, v

In use, tank 10 is filled with aqueous liquid to level 33, spiral 12 is set in motion, magnet means 70 is actu-' ated and belt 71 is set into rotation. An aqueous slurry or pulp, containing relatively coarse, relatively non magnetic iron ore particles and relatively fine magnetic ferrosilicon particles is continuously fed from feed trough 31 over weir 82 into the inlet end of space 76 and into the Zone of attractive force of magnet means 78, the direction of movement of the feed being concurrent with that of belt 71. The ferro-silicon particles of the "cod are attracted to belt 71 and are carried past gap 7'7 and past the outer edge of feed plate 75, at which latter locus the particles have been moved out of the zone of attractive force of magnet means 70 and may be removed from the belt 71 and transferred to concentrate launder 31 by the aid of a spray of water from spray means 85. The relatively non-magnetic iron ore particles of the feed, not being attracted to belt 71, tend to settle toward feed plate 74 and when they reach 77 they descend through the latter into the pool end of tank 10 and settle into the zone of influence of spiral 12!. The so-settled iron ore particles are gradually moved, by spiral 12, up the inclined bottom of tank and above the water level 33 to effect a substantial de- Watering of the non-magnetic particles before the same are discharged from the apparatus as concentrated iron ore freed from associated ferro-silicon.

The ferro-silicon concentrate caught in launder 31 is moved to suitable apparatus, not shown, for reforming heavy medium therefrom to constitute the heavy medium of a float-sink operation for separating hematite particles from the gangue of a lean iron ore material.

I claim:

1. Apparatus for separating fine magnetic particles from associated relatively coarse non-magnetic particles of a pulp product of the sink-float type, which comprises a tank having an inclined bottom of trough-like configuration, means for discharging liquid and fine sands from said tank to maintain a substantially constant level of liquid therein, an Archimedes screw arranged for rotation adjacent the surface of the bottom of said tank, the high ends of said screw and said tank bottom extending above the level maintained by said discharging means, means for rotating said screw, a horizontally disposed water-tight drum mounted for rotation above and adjacent the lower end of said tank and having a portion of its peripheral surface extending below the level maintained by said discharging means, a horizontally disposed feed plate complemental in cross-section to the peripheral surface of said drum mounted in the tank adjacent the low end thereof the lower portion of said feed plate being disposed below the level maintained by said discharging means, said feed plate and the adjacent surface of said drum defining an arcuate space therebetween, means for rotating said drum, stationary magnet means arranged within said drum to exert attractive force in said arcuate space, means for feeding pulp into said arcuate space, and means adjacent an upper portion of said feed plate and above the level maintained by said discharging means for removing from said drum fine magnetic particles caused to adhere thereto by attractive force of said magnet means, said feed plate having in the lower submerged portion thereof an aperture through which non-magnetic particles of the pulp may pass from said arcuate space directly into the lower portion of said tank for settling into the zone of influence of said Archimedes screw.

2. Apparatus as defined in claim 1, in which said feed plate and said drum are disposed longitudinally of said tank and in such relation to the latter that said magnetic particles-removing means overlies a side of said tank.

3. Apparatus as defined in claim 1, in which the pulpfeeding means is arranged and adapted to deliver a stream of the pulp into said arcuate space in a direction counter to the direction of rotation of said drum.

4. Apparatus as defined, in claim 3, in which the pulpfeeding means is arranged and adapted to deliver the pulp stream at a locus intermediate said magnetic particles-removing means and said aperture.

5. Apparatus as defined in claim 1, in which the discharging means consists essentially of a launder so associated with that side of said feed plate which is remote from said magnetic particles-removing means as to receive fluid overflowing said tank by way of that portion of said arcuate space which is adjacent said feed plate side whereby all fluid overflowing said tank passes through the zone of attractive force of said magnet means.

6. Apparatus as defined in claim 1, in which the pulpfeeding means is arranged and adapted to deliver a stream of the pulp into said arcuate space in the same direcion as the direction of rotation of said drum and at a locus remote from said magnetic particles-removing means.

7. Apparatus as defined in claim 6, in which said feed plate and said drum are disposed longitudinally of said tank and in such relation to the latter that said magnetic particles-removing means overlies a side of said tank.

8. Apparatus as defined in claim 7, in which said discharging means comprises (l) a weir associated with that side of the tank which said magnetic particles-removing means overlies and positioned beneath the latter, and

- (2) an inclined deflecting plate operatively associated,

along an upper side thereof, with said weir and spaced from and beneath said feed plate to provide in cooperation with the latter a passageway for fluid overflowing said tank, the lower side of said deflecting plate extending to a locus beneath said aperture.

9. Apparatus for separating fine magnetic particles from associated relatively coarse non-magnetic particles of a sink-float product pulp, which comprises a tank having an inclined bottom of trough-like configuration, means for discharging liquid and fine sands from said tank to maintain a substantially constant level of liquid therein, an Archimedes screw arranged for rotation adjacent the surface of the bottom of said tank, the high ends of said screw and said tank bottom extending above the level maintained by said discharging means, means for rotating said screw, a pair of horizontally disposed water-tight drums mounted for rotation above and ad jacent the lower end of said tank and having portions of their peripheral surfaces extending below the level maintained by said discharging means, a pair of horizontally disposed feed plates complemental in crosssection to the peripheral surfaces of said drums mounted in the tank adjacent the low end thereof the lower portions of said feed plates being disposed below the level maintained by said discharging means, said feed plates and the adjacent surfaces of said drums defining arcuate spaces, said feed plates and associated drums being disposed longitudinally of said tank and adjacent opposite sides of the latter, means for rotating said drums in such directions that in each case the rising side of the drum is adjacent the tank, stationary magnet means arranged within each of said drums to exert attractive force in said arcuate spaces, means for feeding pulp into said arcuate spaces in directions counter to the directions of rotation of said drums, and means adjacent an upper side portion of each of said plates and above the level maintained by said discharging means for removing from said drums fine magnetic particles caused to adhere thereto by attractive force of said magnet means, each of said feed plates having in the lower submerged portion thereof an aperture through which non-magnetic particles of the pulp may pass from said arcuate space directly into the lower portion of said tank for settling into the zone of influence of said Archimedes screw,

, said discharging means consisting essentially of a launder so associated with the facing sides of the feed plates as to receive fluid overflowing said tank by way of the adjacent portions of said arcuate spaces whereby all fluid overflowing said tank passes through the zone of attractive force of said magnet means.

10. Apparatus for separating fine magnetic particles from associated relatively coarse non-magnetic particles of a pulp product of the sink-float type, which comprises a tank having an inclined bottom of troughlike configuration, means for overflowing liquid and fine sands from said tank to maintain a substantially constant level of liquid therein, an Archimedes screw arranged for rotation adjacent the surface of the bottom of said tank, the high ends of said screw and said tank bottom extending above the level maintained by said overflowing means, means for rotating said screw, means providing an endless surface to which magnetic particles may be attracted, said endless surface-providing means being horizontally disposed and mounted above and adjacent the lower end of said tank and having a portion of its surface extending below the level maintained by said overflowing means, a horizontally disposed feed plate complemental in cross-section to the lower portion of said endless surface-providing means and mounted in the tank adjacent the low end thereof the lower portion of said feed plate being disposed below the level maintained by said overflowing means, said feed plate and the adjacent surface of said endless surface-providing means defining an arcuate space therebetween, means for traversing said endless surface-providing means, stationary magnet means arranged above the lower surface of said endless surface-providing means, means for feeding pulp into said arcuate space, and means adjacent an upper portion of said feed plate and above the level maintained by said overflowing means for removing from the surface of said endless surface-providing means fine magnetic particles caused to adhere thereto by attractive force of said magnet means, said feed plate having in the lower submerged portion thereof an aperture through which non-magnetic particles of the pulp may pass from said arcuate space directly into the lower portion of said tank for settling into the zone of influence of said Archimedes screw.

No references cited. 

1. APPARATUS FOR SEPARATING FINE MAGNETIC PARTICLES FROM ASSOCIATED RELATIVELY COARSE NON-MAGNETIC PARTICLES OF A PULP PRODUCT OF THE SINK-FLOAT TYPE, WHICH COMPRISES A TANK HAVING AN INCLINED BOTTOM OF TROUGH-LIKE CONFIGURATION, MEANS FOR DISCHARGING LIQUID AND FINE SANDS FROM SAID TANK TO MAINTAIN A SUBSTANTIALLY CONSTANT LEVEL OF LIQUID THEREIN, AN ARCHIMEDES SCREW ARRANGED FOR ROTATION ADJACENT THE SURFACE OF THE BOTTOM OF SAID TANK, THE HIGH ENDS OF SAID SCREW AND SAID TANK BOTTOM EXTENDING ABOVE THE LEVEL MAINTAINED BY SAID DISCHARGING MEANS, MEANS FOR ROTATING SAID SCREW, A HORIZONTALLY DISPOSED WATER-TIGHT DRUM MOUNTED FOR ROTATION ABOVE AN ADJACENT THE LOWER END OF SAID TANK AND HAVING A PORTION OF ITS PERIPHERAL SURFACE EXTENDING BELOW THE LEVEL MAINTAINED BY SAID DISCHARGING MEANS, A HORIZONTALLY DISPOSED FEED PLATE COMPLEMENTAL IN CROSS-SECTION TO THE PERIPHERAL SURFACE OF SAID DRUM MOUNTED IN THE TANK ADJACENT THE LOW END THEREOF THE LOWER PORTION OF SAID FEED PLATE BEING DISPOSED BELOW THE LEVEL MAINTAINED BY SAID DISCHARGING MEANS, SAID FEED PLATE AND THE ADJACENT SURFACE OF SAID DRUM DEFINING AND ACTUATE SPACE THEREBETWEEN, MEANS FOR ROTATING SAID DRUM, STATIONARY MAGNET MEANS ARRANGED WITHIN SAID DRUM TO EXERT ATTRACTIVE FORCE IN SAID ARCUATE SPACE, MEANS FOR FEEDING PULP INTO SAID ARCUATE SPACE, AND MEANS ADJACENT AN UPPER PORTION OF SAID FEED PLATE AND ABOVE THE LEVEL MAINTAINED BY SAID DISCHARGING MEANS FOR REMOVING FROM SAID DRUM FINE MAGNETIC PARTICLES CAUSED TO ADHERE THERETO BY ATTRACTIVE FORCE OF SAID MAGNET MEANS, SAID FEED PLATE HAVING IN THE LOWER SUBMERGED PORTION THEREOF AN APERTURE THROUGH WHICH NON-MAGNETIC PARTICLES OF THE PULP MAY PASS FROM SAID ARCUATE SPACE DIRECTLY INTO THE LOWER PORTION OF SAID TANK FOR SETTLING INTO THE ZONE OF INFLUENCE OF SAID ARCHIMEDES SCREW. 